1. Field of the Invention
The present invention relates to a sliding-vane rotary compressor for use mainly in automobile air-conditioners.
2. Description of the Prior Art
With the trend toward reduction in weight of automobiles, a demand has been created for a lightweight compressor for automobile air-conditioners. To cope with this demand, the material constituting parts defining a compression chamber has been changed to aluminum.
In sliding-vane rotary compressors, a front side block and a rear side block on which bearings are mounted for rotatably supporting the drive shaft of a rotor are made from aluminum or an aluminum alloy. Since aluminum has a relatively large thermal expansion coefficient, the front and rear side blocks made of aluminum are likely to thermally expand when subjected to a high temperature in the vicinity of the drive shaft. As a result, the clearance (bearing clearance) between the drive shaft and each of the bearings is enlarged or widened. One solution to this problem is disclosed in Japanese Utility Model Application No. 63-169271, in which rings of ferrous metal are press-fitted around the respective bearings to limit the thermal expansion of the front and rear side blocks in the vicinity of the bearings. The ferrous metal rings or bushings also under-go thermal expansion when the temperature in the vicinity of the drive shaft is elevated. With this thermal expansion, the bearing clearance is enlarged with the result that an unpleasant operation noise is generated. In addition, the ferrous metal rings are relatively heavy and hence do not meet with the reduced weight requirements of the modern compressor.